TITLE: Example of protected inheritance

PROBLEM: anderson@Software.Mitel.COM (David Anderson)

I am curious as to the use of protected inheritance. When would one use
such a construct?


RESPONSE: grumpy@cbnewse.cb.att.com (Paul J Lucas), 12 Jan 94
		  AT&T Bell Laboratories


The all-time, canonical example (if I had a nickel...):

	class List {};
	class Set : protected List {};
	class Map : protected Set {};

Here, Set is implemented-in-terms-of-a [Map] and Map is
implemented-in-terms-of-a [List].  Map may need to use some members
of List to do its thing; hence, the only solution for this
example is to use protected inheritance.